1. Field of the Invention;
This invention relates to a switching system comprising a circuit breaker for performing a reclosing operation at a high speed, a grounding device, and an interlocking device for mechanically interlocking the grounding device with the circuit breaker.
2. Description of the Prior Art;
Upon the occurrence of a ground fault in one wire of two wire power transmission lines suspended together from a tower and; operative with high voltage, for example, 1,000 kilovolts, a short circuit current on the order of thousands of amperes may result. At such an occurrence,; even the opening of associated circuit breakers at both ends of the one short-circuited wire of; the two power transmission lines does not readily result in the extinction of an electric are of a small current on the order of tens of amperes caused by; an induced voltage from the other wire of the power transmission lines. Thus, if the circuit breakers perform the high speed reclosure operation then the high voltage is applied to the one wire before the extinction of the electric arc at the fault point. This results in the fault again occurring. To avoid this objection, it has been a conventional practice to disconnect a failed transmission line from a mating electric source by associated circuit breakers after which an associated high speed operating grounding device is immediately closed to reduce the particular induced voltage to extinguish an electric arc at a fault point and then the circuit breaker is reclosed at a high speed. For example, the grounding device has been able to be closed at a high speed corresponding to about five cycles of the system current after the interruption by the circuit breakers and to be put in its closed position for a time interval corresponding to about fifteen cycles of the system current after which the grounding device is opened at a high speed corresponding to about five cycles of the system current. Thereafter the occurrence of a malfunction might result in a ground fault. Thus it is desirable to provide an interlocking device for enabling the operation of an operating mechanism for the grounding device for a time interval of from 0.5 to 1 second immediately after the opening of the circuit breakers but disabling the operation thereof for the remaining time interval.
This measure can be electrically accomplished by applying electrical signals to the operating mechanisms for the circuit breakers and grounding device through delayed relays to initiate the operations thereof respectively. Alternatively a mechanical interlocking device may be used for the same purpose in order to provide for the safety thereof. In the latter case it is desirable to provide a mechanical interlocking device prevented from adversely affecting the operation of the circuit breakers due to its being out of order.
Accordingly it is an object of the present invention to provide a new and improved switching system prevented from malfunctioning by the provision of a mechanical locking device for enabling the operation of a grounding device involved only for a predetermined short time interval immediately after the opening of an associated circuit breaker which is reclosable at a high speed.